1. Field of the Invention
The invention relates to methods and apparatus for replacing studs damaged after emplacement in existing equipment.
In another respect, the invention relates to a method and apparatus for replacing damaged studs wherein the threaded diameter of the original stud is retained so that no modification of clearance hole diameters is required on the part held by said original stud.
In yet another respect, the invention relates to a method and apparatus for replacing a damaged stud whereby the replacement stud may be emplaced at proper torque levels using conventional, non-specialized tools.
In a more particular aspect, the invention relates to the use of a replacement stud having a first threaded segment identical to that of the original stud and a second threaded segment whose diameter is predetermined by the size of the drill selected to counterdrill the damaged stud from the original stud hole.
In a still more particular aspect, the invention relates to a dual diameter replacement stud having a frangible, necked-down diameter surmounted by a suitable drive head for use with conventional, hand or power drive tools such that the drive head will snap from the replacement stud when the replacement stud is emplaced in the equipment at the proper torque level.
2. Description of the Prior Art
Prior art techniques for replacing damaged studs usually take one of two approaches. In one, a hole smaller in diameter than that of the original stud is drilled through the damaged stud along its central axis. A special form of tap, having a left-hand thread, is then driven down into the drilled hole. When the tap bottoms out, the operator continues turning the tap, which action now tends to ease the broken segment of the original stud out of the stud hole. A new "original equipment" stud may then be used to make the necessary repair.
Unfortunately, most repair facilities find themselves without such specialized stud removal taps. These left-handed tools are relatively expensive, they must be stocked in multiple sizes, and they are prone to breakage while in use in easing the broken stud segment out of the stud hole. This compounds the repair job since these taps are of hardened steel and counterdrilling them is much more difficult than drilling down through a broken stud segment.
Most repair facilities take another approach. The broken stud segment is counterdrilled using a drill having a larger diameter than that of the original stud. This removes the broken segment, but also enlarges the stud hole. This larger hole is then tapped and a new, but larger diameter, stud is emplaced in the hole.
This latter approach leads to additional problems, however. Assume the oversized replacement stud was installed in the wheel hub of a car. The car wheel is held in place on the hub by passing the hub studs through clearance holes in the wheel and then fastening the hub and wheel together using wheel nuts threaded onto the hub studs. But, with an oversized stud in the hub, the wheel cannot be mounted because the new stud will not clear the wheel mounting holes. If one of the wheel holes may be safely enlarged, which, in itself, is problematical, the wheel and hub may be assembled, but proper orientation must now be observed. Also, the wheel is now specialized for use solely with that particular hub and has lost its former versatility.